This invention relates generally to the field of gear locking mechanisms. In particular, this invention relates to a gear locking mechanism designed to releasably lock a steering column.
Today""s steering columns are adjustable in order to allow for an operator of any size to comfortably steer a vehicle. A steering column must be easily adjustable yet be lockable so that it does not move unless the operator releases the lock and manually adjusts the position of the steering column. However, a locking mechanism must also be able to resist the force applied to the steering column in a crash situation, where a force many times greater than that required for normal adjustment is spontaneously applied.
Historically, locking mechanisms have utilized either friction methods or mechanical methods to releasably lock the telescoping steering column in place. Both the friction and the mechanical mechanisms may be applied to releasably lock the steering column in both the telescoping direction and the rake, or tilt direction. Friction methods are considered to be more adjustable, allowing for an almost infinite number of positions of the steering column. The column can be telescoped toward or away from the operator in any increment. When the desired position is achieved, the operator engages a locking device that applies friction in a way that resists force applied to the column. To adjust the column, the user releases the friction lock. However, in the event of a crash, the force applied to the column is often greater than the holding capacity of the friction lock and the steering column can move, possibly causing injury to the operator.
The mechanical method of releasably locking the steering column in place is less adjustable, but provides a stronger lock that resists force more effectively than many friction locks. A mechanical lock can typically be locked only in a finite number of positions, and therefore increases the complexity of the design by requiring the design to have numerous regimented positions for the lock to engage. For a mechanism to resist force applied to a column, interference of the moving and stationary surfaces must occur. This is often accomplished utilizing gear teeth in a ratcheting or rack arrangement. However, the teeth must be strong enough to resist the shear force applied during a crash situation when the steering column moves against the teeth. While such teeth may exhibit sufficient strength to withstand most crash situations, it is still preferred to have a stronger locking structure.
The present invention satisfies the need for a stronger friction locking mechanism while maintaining an easily manufactured design and a wide range of adjustment positions. In one embodiment of the present invention, a steering column locking mechanism is provided comprising a stationary tube with a movable tube telescopically positioned over it. A plurality of teeth is provided on the outer surface of the movable tube that mesh with teeth defined on the outer diameter of a ring-shaped gear. The ring-shaped gear has an axial opening defined therein and first and second camming pins capable of being arranged in both an unlocked and a locked position are placed within the opening of the gear.
In another embodiment of the present invention, a locking mechanism is provided comprising a ring-shaped gear with teeth on its outer diameter and a second set of teeth for the teeth on the ring-shaped gear to intermesh. First and second camming pins are provided and mounted within an axial opening in the ring-shaped gear. Further, a reduced cross-sectional extension is provided on an end of the first camming pin and a reduced cross-sectional extension with an angular section removed therefrom is provided on an end of the second camming pin. The camming pins are mounted so that the rotation of one of the camming pins causes the camming pins to move away from the axis of rotation.
In yet another embodiment of the invention, a method for releasably locking a steering column is provided comprising the steps of providing a movable tube with teeth on its outer surface positioned over a fixed tube and providing a gear with teeth that intermesh with the teeth on the movable tube. First and second camming pins are mounted within an axial opening in the gear. The method further comprises the step of allowing for the rotation of the second pin relative to the gear and the first pin to alternatively apply and release pressure to the interior walls of the gear and prevent rotational movement of the gear.